Magistrate Graham Higgins also ordered him to complete 120 hours' community service, a 12-month youth rehabilitation order and observe a curfew between 7pm and 6am for three months.

The court heard that the boy, who cannot be named for legal reasons, wrote the message at 9.45am on 9 August. It read: "I think we should start rioting, it's about time we stopped the authorities pushing us about and ruining this country.

"It's about time we stood up for ourselves for once. So come on rioters – get some. LOL."

Prosecutor Lucy Miller said the college student had 400 friends on Facebook, some of whom replied to the message calling him an idiot.

She said: "The police were alerted and when they arrived he had already deleted the post."

Defence solicitor Paul Booty called on the magistrates not to be influenced by hysteria surrounding the recent disorder.

He added: "There has been a strong kneejerk reaction and lots of misinformation, including apparent orders, which turned out not to be true, that all parties should be given custodial sentences.

"My concern, not necessarily for this case but for cases up and down the country, is that there will also be an awful lot of appeals."

He said his client, who has a previous conviction for actual bodily harm, had made a mistake and the comment had been a foolish prank.

The boy's mother told the court: "He is normally a good boy but, like all teenagers, he has his stupid moments."

Speaking to magistrates, the boy added: "I meant it as a joke which is why I wrote LOL at the end."

Higgins said that custody had been at the forefront of his mind but that the curfew order would act as "custody at home".